The present invention relates to an apparatus for controlling the friction between the leaf springs of a laminated leaf spring assembly in accordance with the state of a body to be supported.
A laminated leaf spring assembly comprising a number of leaf springs is widely used for suspending a body, e.g. the body of a large vehicle such as a truck or a bus. When the laminated leaf spring assembly suspends the body of a vehicle, the driver's comfort and the driving stability of the vehicle depend on the spring constant of the assembly and the friction between the leaf springs of the assembly. Of course they depend on the condition of the road as well. When the vehicle runs on a smooth road, the smaller the friction between the leaf springs, the more comfort the driver will have. However, the larger is the friction between the leaf springs, the more easy it is for the driver to drive the vehicle. The driver's comfort is considered more important than the driving stability of the vehicle as long as the vehicle runs on a smooth road. This is because a sufficient driving stability is ensured unless the steering wheel needs to be suddenly turned.
In order to increase the friction between the leaf springs, the leaf springs are clamped together by a clamping means at both end portions. The known clamping means is bolts and can clamp the leaf springs tight enough to increase the friction to such extent that the driver's comfort is ensured while the vehicle runs on a rough road. However, the bolts do not help to give the driver comfort while the vehicle runs on a smooth road.